The unicellular freshwater cyanobacterium Synechocystis sp. PCC 6803 is capable of using dihydroxamate xenosiderophores, either ferric schizokinen (FeSK) or a siderophore of the filamentous cyanobacterium Anabaena variabilis ATCC 29413 (SAV), as the sole source of iron in the TonB-dependent manner. The fecCDEB1-schT gene cluster encoding a siderophore transport system that is involved in the utilization of FeSK and SAV in Synechocystis sp. PCC 6803 was identified. The gene schT encodes TonB-dependent outer membrane transporter, whereas the remaining four genes encode the ABC-type transporter FecB1CDE formed by the periplasmic binding protein FecB1, the transmembrane permease proteins FecC and FecD, and the ATPase FecE...

Multicellular organisms must carefully regulate the timing, number, and location of specialized cellular development. In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, nitrogen-fixing heterocysts are interspersed between vegetative cells in a periodic pattern to achieve optimal exchange of bioavailable nitrogen and reduced carbon. The spacing between heterocysts is regulated by the activity of two developmental inhibitors: PatS and HetN. PatS functions to create a de novo pattern from a homogenous field of undifferentiated cells, while HetN maintains the pattern throughout subsequent growth...

We study the surface diffusion of the model cyanobacterium Synechocystis sp. PCC6803 during the incipient stages of cell contact with a glass surface in the dilute regime. We observe a twitching motility with alternating immobile tumble and mobile run periods, resulting in a normal diffusion described by a continuous-time random walk with a coefficient of diffusion D. Surprisingly, D is found to decrease with time down to a plateau. This is observed only when the cyanobacterial cells are able to produce released extracellular polysaccharides, as shown by a comparative study between the wild-type strain and various polysaccharides-depleted mutants...

Bisphenol A has attracted worldwide attention due to its harmful effects on humans, animals and plants. In this study, the toxicological effects of BPA on Cylindrospermopsis raciborskii were assessed based on chlorophyll a ﬂuorescence and transcriptome analyses. The results showed that the growth of C. raciborskii was significantly inhibited when BPA exceeded 0.1 mg L-1 . A marked rise of phase J was observed at a concentration greater than 0.1 mg L-1 , while a K phase appeared at 20 mg L-1 . The chlorophyll a ﬂuorescence parameters of RC/CS0 , F0 , φP0 , φE0 , and ψ0 , underwent a significant decline under all treatments of BPA, whereas a significant increase in both VJ and M0 occurred under all concentrations of BPA...

Kakeromamide A (1), a new cyclic pentapeptide encompassing a thiazole ring moiety and a β-amino acid, was isolated from the marine cyanobacterium Moorea bouillonii. Its structure was elucidated by the spectral analysis and the modified Marfey's method. Compound 1 induced differentiation of neural stem cells into astrocytes at the concentration of 10 µM.

In the present paper, Mössbauer spectroscopic studies of dry biomass samples of the cyanobacterium Arthrospira platensis (formerly known as Spirulina platensis) were performed with regard to metabolic iron accumulation. 57 Fe Mössbauer parameters of iron in the biomass correspond to ferrihydrite. Spectra of iron hydroxides in A. platensis biomass differ from those of iron complexes with ethylenediaminetetraacetic acid injected to Zarrouk culture medium. The limit of saturation of A. platensis trichomes with iron in the form of ferrihydrite was found to be 5 μg/ml (0...

Cyanobacterial blooms and their associated toxins are growing issues for many aquatic resources, and pose a major threat to human health and ecological welfare. To control cyanobacterial blooms and their toxins, the efficacy of a newly developed granular compound (sodium carbonate peroxyhydrate 'SCP', trade name 'PAK® 27' algaecide) containing hydrogen peroxide (H2 O2 ) as the active ingredient was investigated. First, the dose efficacy of the SCP that corresponded to 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0 and 8...

Arthrospira platensis , better known as Spirulina, is one of the most important microalgae species. This cyanobacterium possesses a rich metabolite pattern, including high amounts of natural pigments. In this study, we applied a combined strategy based on Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) and Ultra High-Performance Liquid Chromatography (UHPLC) for the qualitative/quantitative characterization of Spirulina pigments in three different commercial dietary supplements. FT-ICR was employed to elucidate the qualitative profile of Spirulina pigments, in both direct infusion mode (DIMS) and coupled to UHPLC...

Morphological transformations in primitive organisms have long been observed; however, its biomechanical roles are largely unexplored. In this study, we investigate the structural advantages of dimorphism in Arthrospira platensis, a filamentous multicellular cyanobacterium. We report that helical trichomes, the default shape, have a higher persistence length (Lp), indicating a higher resistance to bending or a large value of flexural rigidity (kf), the product of the local cell stiffness (E) and the moment of inertia of the trichomes' cross-section (I)...

Transfer of nitrogen fixation ability to plants, especially crops, is a promising approach to mitigate dependence on chemical nitrogen fertilizer and alleviate environmental pollution caused by nitrogen fertilizer run-off. However, the need to transfer a large number of nitrogen fixation (nif) genes and the extreme vulnerability of nitrogenase to oxygen constitute major obstacles for transfer of nitrogen-fixing ability to plants. Here we demonstrate functional expression of a cyanobacterial nitrogenase in the non-diazotrophic cyanobacterium Synechocystis sp...

Pili are found on the surface of many bacteria and play important roles in cell motility, pathogenesis, biofilm formation, and sensing and reacting to environmental changes. Cell motility in the model cyanobacterium Synechocystis sp. PCC 6803 relies on expression of the putative pilA9-pilA10-pilA11-slr2018 operon. In this study, we identified the antisense RNA PilR encoded in the noncoding strand of the prepilin-encoding gene pilA11 . Analysis of overexpressor [PilR(+)] and suppressor [PilR(-)] mutant strains revealed that PilR is a direct negative regulator of PilA11 protein...

The authors' objectives are to investigate the therapeutic effect of alkaloid extract of cyanobacteria Spirulina platensis on the lipid profile of hypercholesterolemic male rabbits and to identify the active compounds in the alkaloid extract. Male rabbits were divided into four groups of six animals. The intact rabbits in the first group served as a negative control. The second group served as a positive control (hypercholesterolemic rabbits). Over a 4-week period, hypercholesterolemic rabbits in the third group received a low dose of alkaloid extract (33 mg/kg), and the hypercholesterolemic rabbits in the fourth group received a high dose (66 mg/kg)...

The study of enzyme substrate specificity is vital for developing potential applications of enzymes. However, the routine experimental procedures require lot of resources in the discovery of novel substrates. This article reports an in silico structure-based algorithm called Crius, which predicts substrates for enzyme. The results of this fragment-based algorithm show good agreements between the simulated and experimental substrate specificities, using a lipase from Candida antarctica (CALB), a nitrilase from Cyanobacterium syechocystis sp...

Accurate quantification of Mass Isotopologue Distribution (MID) of metabolites is a prerequisite for 13C-metabolic flux analysis. Currently used mass spectrometric (MS) techniques based on multiple reaction monitoring (MRM) place limitations on the number of MIDs that can be analyzed in a single run. Moreover, the deconvolution step results in amplification of error. Here, we demonstrate that SWATH MS/MS, a data independent acquisition (DIA) technique allows quantification of a large number of precursor and product MIDs in a single run...

The aquatic cyanobacterium Nostoc verrucosum forms macroscopic colonies in streams, and its appearance is superficially similar to that of the terrestrial cyanobacterium Nostoc commune. N. verrucosum is sensitive to desiccation, unlike N. commune, although these Nostoc cyanobacterial species share physiological features, including massive extracellular polysaccharide production and trehalose accumulation capability. In this study, water-soluble sunscreen pigments of mycosporine-like amino acids (MAAs) were characterized in N...

Coccoid green algae can be divided in two groups based on their cell wall structure. One group has a highly chemical resistant cell wall (HR-cell wall) containing algaenan. The other group is more susceptible to chemicals (LR-cell wall - Low resistant cell wall). Algaenan is considered as important molecule to explain cell wall resistance. Interestingly, cell wall types (LR- and HR-cell wall) are not in accordance with the taxonomic classes Chlorophyceae and Trebouxiophyceae, which makes it even more interesting to consider the ecological function...

A novel halotolerant species of cyanobacterium of the order Chroococcales was isolated from hypersaline estuary in Kwa-Zulu Natal, South Africa. A comprehensive polyphasic approach viz., cell morphology, pigment composition and complete genome sequence analysis was conducted to elucidate the taxonomic position of the isolated strain. The blue-green oval to rod-shaped cells were 14-18 μm in size, and contained a high amount of phycocyanin pigments. The strain was moderate thermotolerant/alkalitolerant halophile with the optimum conditions for growth at 35 °C, pH 8...

Changes in the redox state of the photosynthetic electron transport chain act as a signal to trigger acclimation responses to environmental cues and thioredoxin has been suggested to work as a key factor connecting the redox change with transcriptional regulation in the cyanobacterium Synechocystis sp. PCC 6803. We screened for redox-dependent transcription factors interacting with thioredoxin M (TrxM) and isolated the GntR-type transcription factor Sll1961 previously reported to be involved in acclimation responses of the photosynthetic machinery...